Fuse cutout



G. L. HILL FUSE CUTOUT March 10, 1959 2 Sheets-Sheet 1 Filed Aug. 18,1954 United States Patent FUSE CUTOUT George Leslie Hill, Oakland,Calif.

Application August 18, 1954, Serial No. 450,575

Claims. (Cl. 200-114) My invention relates to fuse cutouts; and moreparticularly to fuse cutouts of the open, dropout type used inrelatively high voltage distribution circuits.

One of the objects of my invention is the provision of a dropout typefuse cutout capable of efliciently interrupting small, low power factorcurrents without impairment of circuit interruption at high shortcircuit currents.

Another object of my invention is the provision of an open type cutoutin which the various component parts on both terminal ends are shieldedfrom the elements.

Still another object of the invention is the provision of means for moreeificiently retaining the fuse cutout operatively interposed in anelectrical circuit.

Still another object is the provision of an improved latch and trippingmechanism which requires a relatively small force to retain a relativelylarge force in the stored energy position of the operating spring.

A still further object is the adaptation of a deionizing and catchingchamber on the expulsion end of the expulsion tube to operateefiiciently in cooperation with the other improvements of the device.

The invention possesses other objects and features of value, some ofwhich, with the foregoing, will be apparent from the followingdescription and the drawings.

Referring to the drawings:

Fig. l is a side elevational view of the fuse cutout in operativeposition. Portions of the device are broken away to disclose theunderlying structure.

Fig. 2 is a horizontal sectional view taken in the plane indicated bythe line 2-2 of Fig. 1.

Fig. 3 is a vertical sectional view taken in the plane indicated by theline 3-3 of Fig. 2. The view shows the relationship of the parts afterthe fuse link has ruptured.

Fig. 4 is a fragmentary view partly in vertical section showing amodified construction of the lower end of my fuse cutout.

Fig. 5 is a view in elevation taken in the direction indicated by thearrow 5 in Fig. 4.

Fig. 6 is an elevation of the lower guide ferrule removed from theassembly shown in Figs. 4 and 5.

Broadly considered, the open type dropout fuse cutout of my inventioncomprises an expulsion tube equipped with upper and lower terminal endseach shielded from the elements, and provided with the conventional fuselink adapted to be interposed in an electrical distribution line. Meansare provided on the inside of the expulsion tube for automaticallyaccommodating variations in expulsion pressures, and a deionizing andcatching chamber is provided to catch the ruptured and expelled fuselink parts. A trunnion bearing on the lower terminal and carried by aninsulator, provides means for supporting the cutout tube in operativeposition while also providing ice In greater detail then, and referringnow to the drawings, my drop-out type fuse cutout assembly comprises theconventional insulator 2 provided with a center bracket 3 for attachmentto a cross arm or other support. The bracket is designed so that theinsulator is supported at the typical angle with respect to the verticalaxis used for dropout cutouts.

Secured to the top and bottom ends of the insulator are clamping rings 4and 6, providing a mounting for the terminal brackets 7 and 8respectively. High voltage electrical leads 9 and 12 connect to theterminal brackets 7 and 8 respectively.

' tube when the fuse link ruptures due to an overload or short circuit,the lower end of the expulsion tube is provided with trunnions 21journaled in the bearing bracket 22, which, in turn is secured to thesupporting bracket 8 on the insulator 2.

For ease and economy of construction and assembly of the device, thetrunnions are fixed on a cantilever bracket arm 23 integral with thecylindrical expulsion tube guide member 24. The guide member and bracketarm 23 are preferably cast in one integral unit.

The guide member is preferably of such inside diameter as to easilyaccommodate the coil spring 26 therein, which in the assembly fitsaround the lower end of the expulsion tube 16 and works between collarrings 27 and 28 shown in Fig. 3.

The collar ring 27 is secured within the upper end of the cylindricalguide member 24 by screws 29, and closely surrounds the expulsion tubewhich is slidable therethrough.

In Fig. 3 the collar ring 28 is adjustably secured to the tube 16 by setscrews 31, and is proportioned to fit slidably within the guide member24.

Thus, it will be seen by reference to Figs. 1 and 3, that upwardmovement of the expulsion tube compresses the spring until the parts arein the position shown in Fig. 1. This is the position the parts are inwhen the cutout is fused and ready to be inserted in the circuit.

Secured to the lower end of the expulsion tube as by threads 32, is aferrule 33 provided with an annular flange 34 and a cylindrical threadedextension 36 adapted to engage the threads 37 of a catching anddeionizing chamber 38. A notch 39, formed in the flange 34 and threadedextension, provides for the passage therethrough of the outer portion ofthe pigtail or flexible conductor. The end of the flexible conductor islooped around the threaded stud 41, fixed on the pivotally mounted latchplate 42. A terminal thumb nut 43 is shown in Figs. 1 and 3 to insurepositive contact and anchoring of the pigtail. It should be noted thatbefore the pigtail is anchored to the latch plate, at the terminal thepigtail is passed over the bifurcated end 44- of the latch plate.

for pivotal movement of the cutout expulsion tube when I the fuse linkruptures due to an overloaded circuit. Means are provided on the lowerend of the expulsion tube for retaining the fuse cutout operativelyengaged in the circuit, and for quickly separating the upper terminalend from the line terminal when the fuse link ruptures.

The latch plate, shown best in Figs. 1 and 3, is pivotally mounted onthe guide member by means of the pin 46 journaled in bearing tabs 47.Spaced below the pivot point-and extending laterally from the latchplate in cantilever fashion is a latch stud 48. When the'cutout is inloaded condition, as shown in Fig. 1, the latch stud extends through theaperture 49 in the guide member, and the proportions of the parts aresuch that the latch' stud underlies the collar ring 28, which has beenmoved upwardly to a point determined by the 3 length of the fully loadedspring. When the parts are in this position, that is, with the latchunderlying the collar ring 28 and the spring fully loaded, the pigtailis pulled taut and anchored under terminal thumb nut 43.

Thus, it will be apparent that downward pressure on the expulsion tubeexerted by the spring results in a rotary movement being applied to thelatch plate, tending to rotate it counter-clockwise to the positionshown in Fig. 3. counteracting this rotary movement and tending to holdthe latch and latch stud engaged, is the tension in the pigtail beingapplied at the bifurcated end 44 of the latch plate. As a result, thehorizontal force exerted on the end of the latch plate is only a smallpercentage of the downward force exerted by the spring. Hence, when thefuse link ruptures, tension in the pigtail immediately drops to zero andthe overwhelming pressure exerted by the spring throws the latch studout of engagement and the parts instantly assume the position shown inFig. 3. It will be readily apparent that the strain imposed on the fuselink is very small as substantially all of the force exerted by thespring is sustained by the pin 46.

When an overload or short circuit occurs and the fuse link ruptures, theresultant arc and combustion of the fuse link parts generates anexceedingly high pressure within the expulsion tube. Since the cap 17closes off the upper end of the expulsion tube, the pressure must berelieved downwardly. Since it is desirable that the fuse link parts beexpelled from the tube, the pressure generated is utilized for thatpurpose. The deionizing and catching chamber 38 catches these molten andhot parts, while providing for the cooling and subsequent escape of thegases.

Tests and field experience have shown that typical expulsion cutoutswithout the deionizing and catching chambers will usually expel the fuselink and flexible conductor with a sufficiently high velocity to pull itloose from the terminal thumb nut 43 at the bottom of the cutout when aheavy short circuit occurs. If the link is allowed to fall to the groundin a rural area during the dry season it constitutes a fire hazard andmay start a disastrous grass and forest fire or it may hit a person orautomobile if in an industrial area.

A light fault current may expel the fuse link and pigtail from the tubebut on cutouts without the deionizing and catching chamber it will bedangling from the bottom terminal. If another fuse on the sametransformer bank or capacitor bank remains intact the dangling fuse linkand conductor will be energized from this other source. A dangling fuselink and conductor is not readily visible, particularly on dark orstormy nights (when a large percentage of fuse blowings occur) and itconstitutes a hazard to the man who must climb the pole to replace theblown fuse. Therefore the adaptation of the deionizing and catchingchamber to the dropout cutout is a distinct improvement on this type ofdevice.

It has been found through experience with this type of cutout thatexpulsion tubes having an internal diameter of the order of about /2" or25 are very etficient in expulsion of fuse link parts when high shortcircuiting currents are involved. However, when low currents at lowpower factors, such as in highly inductive circuits and in circuitshaving capacitors as the load, are involved, the expulsion tubes oflarge inside diameter have proved to be inefficient, with a resultantprolongation of the arcing interval, resulting in failure of the deviceto interrupt the circuit in some cases.

I have discovered that the solution of this problem lies in control overthe time-pressure ratios at the instant of interruption and shortlythereafter. Thus, in a large inside diameter expulsion tube,interruption of a high short circuiting current results in the generatedpressure rising to a peak very rapidly in point of time, and thentapering 01f gradually as the relatively large inside diameter allowsthe gases to escape. If an expulsion tube having a relatively smallinside diameter, say about or A or less is used with the same current,the rapid build-up of pressure and the relatively restricted escape pathresults in a pressure that will burst the expulsion tube.

On the other hand, small low power factor currents do not generatesufiiciently high pressures, and the large inside diameter of the tubesallows escape of the gas at a relatively low velocity, in some cases thepressure and velocity combination not being sufficient to expel the fuselink parts. Thus, the industry has resorted to different size cutoutsand designs to handle the variations in circuit conditions andoverloads.

To obviate this problem, the cutout of my invention is provided with anexpulsion tube which will operate safely and efficiently in eithercircumstance. As shown in Figs. 1 and 4, the inside surface of the tube16 is formed with a wide and relatively deep spiral groove 51 in thenature of a thread extending the length of the tube.

In high short circuit current interruption, the spiral groove providesthe necessary volume for safe expansion and escape of the gases underhigh pressure conditions before the fuse link parts are expelledentirely from the tube. This portion of the gases escaping spirally downthe groove, are cooled as they go, due to the increased length oftravel. The rest of the gases are expelled straight down at considerablevelocity due to the restricted passage and operate to expel the fuselink parts from the tube.

In small low power factor currents, while the pressure generated is notas great, the relatively restricted escape passages acts to maintain ahigh escape velocity in the gases, thus completely expelling all fuselink parts.

In Figs. 4, 5 and 6 I have shown a modified form of the lower part ofthe cutout, especially the ferrule 33, and a modified means foranchoring the end of the pigtail.

The guide ferrule 33 in these figures differs from that shown in Figs. 1and 3 only in that the upper end has been extended and is provided atits top with a groove 52 to receive a snap ring 53. This form eliminatesthe collar 28 on the tube 16. The tube 16 is guided in the guide member24 by the aperture 54 therein and the ring 56. This base ring 56 isslideable within the guide member 24 and provides a base against whichthe lower end of the spring 26 may abut. The snap ring 53 has sufficientclearance between its outside diameter and the inside diameter of guidemember 24 to be expanded and then snap into the groove 52. The snap ringacts as a stop for the ferrule 33 as it slides through the aperture 54in guide member 24. If desired the base ring 56 may be eliminated andthe spring allowed to abut against the end of the ferrule or directly onthe snap ring. In this case the ring 27 may act as the guide for thetube 16.

There is sometimes a tendency for the expulsion tube and ferrule torotate within the guide member 24. To prevent rotary movement of theparts, a small inwardly projecting lug 57 on the lower end of the guidemember 24 is adapted to project into the vertical groove 58 formed inthe periphery of the ferrule 33.

The modified anchoring means for the pigtail includes a shorter stud 41provided with a nut 59 retaining a spring clip 61 of suitable materialsuch as beryllium copper on the latch plate. Crowding the end of thepigtail between the clip 61 and the plate 42 allows the resilience ofthe clip to act as a clamp and retain the pigtail in a securely anchoredcondition at the terminal.

One of the objects of my present invention is to provide a cutout of thedrop-out type in which means are provided to protect the upper and lowerterminals from the ele ments, particularly salt air spray, sleet and iceformation and highly contaminated industrial atmosphere.

To this end I provide a hood 63 fixed securely to the upper terminalbracket 7 by means of the bolt 64. A re silient contact plate 66,preferably of beryllium copper po sitioned within the hood serves toelectrically and mechanically connect the terminal bracket 7 and thecapped upper end of the expulsion tube to hold it in closed position.The hood is preferably formed with a top 67 and sides 68 which flare outslightly at the bottom; and the extreme outer ends 69 of the sidesproject beyond the top and are flared out to permit easy entrance of thecap 17 therebetween when the tube is inserted in the circuit by means ofthe ring 71.

The guide member 24 and latch mechanism is protected by a hood orhousing 72, having a top 73, a bottom 74, and side walls 77. The top ispreferably bifurcated to accommodate the expulsion tube, and the sidesare provided with the circular sections 77 adapted to enclose andresiliently grip the sides of the guide member 24. It will thus be seenthat sleet, ice and contamination are efifectively prevented fromfouling the operating mechanism, thereby reducing the likelihood of thecutout not operating properly when an overload occurs. It is to beunderstood that I do not limit myself to the embodiments shown anddescribed, but may embody my invention in various forms within the scopeof the appended claims.

I claim:

1. In a fuse cutout of the drop-out type, an expulsion tube, a fuse linkwithin the tube, terminals on the cutout, a guide member pivotallymounted on one of said terminals, said guide member apertured toslidably receive said tube, a collar ring fixed on the expulsion tubeand slideable wholly within said guide member between upper and lowerlimits, a coil spring interposed between said collar ring and the guidemember, and latch means on the guide member adapted to engage saidcollar ring at its upper limit within the guide member to lock thespring in compressed condition.

2. In a fuse cutout of the drop-out type employing an expulsion tubehaving a fuse link and flexible conductor therein for interpositionbetween terminals of said cutout, a guide member pivotally mounted onone of said terminals and slidably enclosing a lower portion of theexpulsion tube, a collar ring fixed on the expulsion tube and slideabletherewith wholly within said guide member between upper and lowerlimits, a coil spring surrounding the tube within the guide member andengaging the collar ring and compressible thereby when the collar ringis at its upper limit within the guide member, a latch pivotally mountedon the guide mmeber and adapted to lock the spring in compressedcondition, and means including said flexible conductor for retaining thecutout in latched condition.

3. In an expulsion fuse cutout assembly of the drop-out type, thecombination comprising an expulsion tube having at least one open end, afuse link in the tube for insertion in an electric circuit, and a spiralgroove within and extending the length of said expulsion tube foraccommodating variations in pressure therein.

4. In a fuse cutout of the drop-out type, an expulsion tube having afuse link therein for interposition between terminals of said cutout; aguide member pivotally mounted on one of said terminals, a collar ringadjustably secured on the expulsion tube and slideable therewith whollywithin said guide member between upper and lower limits therein, a coilspring interposed between said collar ring and the guide member toimpart a downward force on the expulsion tube when the collar ring is atits upper limit within the guide member and the spring is compressed,latch means pivoted on the guide member and projecting thereinto toreleasably lock the collar ring at said upper limit, and a hoodresiliently mounted on the guide member to shield said latch andcomponent parts from the elements in all positions of the cutout.

5. In combination, a dropout fuse cutout comprising upper and lowerterminals mounted on an insulator, a bearing for a trunnion on the lowerterminal, an expulsion fuse tube between the terminals, an aperturedhollow cylindrical guide member enclosing the lower end of the tube andhaving a trunnion, said tube passing longitudinally through said guidemember, a fuse link within the expulsion tube, a collar on the tube, aspring positioned for exerting a downward force on the tube, a trippingmechanism held in restraint by the fuse link, said mechanism including alever arm pivoted on the guide member and in its restrained positionlying substantially parallel to the longitudinal axis of the tube, and alatch on the lever arm positioned to project into said aperture in theguide member and extending under the collar on the tube.

References Cited in the file of this patent UNITED STATES PATENTS Re.20,420 Mangan June 22, 1937 2,151,159 Schultz Mar. 21, 1939 2,223,975Traver Dec. 3, 1940 2,253,719 McMahon Aug. 26, 1941 2,291,646 RamseyAug. 4, 1942 2,291,647 Ramsey Aug. 4, 1942 2,309,013 Rawlins et al. Jan.19, 1943 2,334,134 Steinmayer Nov. 9, 1943 2,462,212 Mosley Feb. 22,1949 2,466,486 Schultz Apr. 5, 1949 2,483,577 Fahnoe Oct. 4, 19492,626,332 Earle et al J an. 20, 1953 2,658,977 Hoye Nov. 10, 1953FOREIGN PATENTS 319,749 Great Britain Dec. 29, 1930

